Research Newsletter-Fall/Winter 2012

BRIEFLY...

Eicosapentaenoic acid (EPA) and docosahexaenoic acid
(DHA) are very long-chain, highly unsaturated fatty
acids derived from alpha-linolenic acid (ALA). ALA is an
essential fatty acid and the parent compound from which
all omega-3 polyunsaturated fatty acids (PUFAs) are made.
Rich dietary sources of ALA are canola oil, flaxseeds, and
walnuts. Though EPA and DHA are generated in the body
from dietary ALA, they can also be obtained directly from
food (especially oily fish) and supplements. The advantage
of increasing EPA and DHA content in cells and tissues to
improve health and prevent disease is an area of intense
research. In particular, the C20-22 omega-3 fatty acids
EPA and DHA, often referred to as “fish oils,” benefit
cardiovascular health by modulating blood lipid levels,
inflammation, and the function of endothelial cells (cells that
line blood vessels) and cardiomyocytes (heart muscle cells).

A recent systematic review and meta-analysis,
published in the Journal of the American Medical
Association (JAMA), concluded that supplementation
with omega-3 PUFAs is not associated with a statistically
significant reduction in the risk of major cardiovascular
events. A meta-analysis is a statistical method that
combines the results from several randomized, clinical
intervention trials (RCTs) that address similar questions.
Combining multiple trials increases the probability of
detecting smaller group differences if present. However,
selection criteria for including or excluding studies can
strongly influence the results of the meta-analysis and
represent an important methodological limitation.
In the present analysis, the authors pooled data on major
cardiovascular events (all-cause mortality, cardiac death,
sudden death, myocardial infarction, and stroke) from 20
RCTs of omega-3 PUFA administration with a combined
total of 68,680 patients.

An emerging theme from the JAMA study, as well as
several other reviews on this topic, is that omega-3
supplementation appears to be better at prevention
(“primary prevention”) than therapy (“secondary
prevention”) of cardiovascular diseases (CVD). Notably,
the vast majority of the pooled RCTs were secondary
prevention trials, meaning that the recruited subjects had
pre-existing CVD or were at increased cardiovascular risk.
Thus, supplementation with omega-3 PUFAs may not
reduce the risk of cardiovascular events in patients with
a history of CVD, particularly when used in combination
with drug therapy, such as statins, aspirin, or anti-hypertensive
medications. However, observational epidemiologic
studies have consistently found that increased fish
consumption or higher omega-3 PUFA blood levels are
associated with a significantly lower risk of cardiovascular
events in healthy adults.

Beyond cardiovascular health, EPA and DHA are
important for visual and neurological development, exert
anti-inflammatory effects, and may slow cognitive decline
with aging (see essential fatty acids). If you do not regularly consume fish, LPI
recommends a two-gram fish oil supplement several times
per week (see Prescription for Health). Consumption
of fish or fish oil may not be suitable for all individuals,
such as vegetarians, vegans, or those with seafood allergies.
Alternative sources of C20-22 omega-3 fatty acids, produced
in yeast or algae, are commercially available.